This security update resolves one publicly disclosed and forty privately reported vulnerabilities in Internet Explorer. The most severe of these vulnerabilities could allow remote code execution if a user views a specially crafted webpage using Internet Explorer. An attacker who successfully exploited these vulnerabilities could gain the same user rights as the current user. Customers whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

The security update addresses the vulnerabilities by modifying the way that Internet Explorer handles objects in memory, by adding additional permission validations to Internet Explorer, by helping to ensure that affected versions of Internet Explorer properly implement the ASLR security feature, and by helping to ensure that cross-domain policies are properly enforced in Internet Explorer. For more information about the vulnerabilities, see the Vulnerability Information section.

The following software versions or editions are affected. Versions or editions that are not listed are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

There are there are multiple update packages listed in the Affected Software table for Internet Explorer 9, Internet Explorer 10, and Internet Explorer 11. Do I need to install all of these updates?Yes. Systems running Internet Explorer 9, Internet Explorer 10, or Internet Explorer 11 will not be fully protected until you have installed both security update 3021952 and the updates for the vulnerability described in Security Advisory 3009008.

If you use Windows Update, Windows Server Update Services (WSUS), or Microsoft Update Catalog to install updates, security update 3021952 will install first. After your system reboots, check for updates again in Windows Update to obtain and install update 3034196.

If you download and install updates manually, you must first install security update 3021952 before installing update 3034196. Failure to install 3021952 before 3034196 can lead to degraded page rendering.

Are there additional updates I should be aware of? Yes. There are additional fixes for Internet Explorer 11 that are included as part of update 3021952.

When you install security update 3021952, updates 3023607 and 3036197 will be installed automatically. Update 3023607 changes TLS protocol renegotiation and fallback behavior. Update 3036197 is required for the Group Policy settings for disabling the SSL 3.0 fallback to appear in all localized languages.

When installation is complete, updates 3021952, 3036197, and 3023607 will be listed in Installed Updates.

If you download and install updates manually, when you click Download, you will be prompted to select updates 3021952, 3023607, and 3036197.

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the February bulletin summary.

In the following table Where specified, Critical, Important, and Moderate values indicate severity ratings. For more information, see Security Bulletin Severity Rating System. Where specified, the abbreviations as shown in the following key indicate maximum impact:

Multiple Memory Corruption Vulnerabilities in Internet Explorer

Remote code execution vulnerabilities exist when Internet Explorer improperly accesses objects in memory. These vulnerabilities could corrupt memory in such a way that an attacker could execute arbitrary code in the context of the current user. The update addresses the vulnerabilities by modifying the way that Internet Explorer handles objects in memory.

An attacker could host a specially crafted website that is designed to exploit these vulnerabilities through Internet Explorer, and then convince a user to view the website. The attacker could also take advantage of compromised websites and websites that accept or host user-provided content or advertisements by adding specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action, typically by getting them to click a link in an instant messenger or email message that takes users to the attacker's website, or by getting them to open an attachment sent through email.

An attacker who successfully exploited these vulnerabilities could gain the same user rights as the current user. If the current user is logged on with administrative user rights, an attacker who successfully exploited these vulnerabilities could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from these vulnerabilities.

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Workarounds

Microsoft has not identified any workarounds for these vulnerabilities.

FAQ

I am running Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, or Windows Server 2012 R2. Does this mitigate these vulnerabilities?Yes. By default, Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted web content on a server. This is a mitigating factor for websites that you have not added to the Internet Explorer Trusted sites zone.

Does EMET help mitigate attacks that could attempt to exploit these vulnerabilities?Yes. The Enhanced Mitigation Experience Toolkit (EMET) enables users to manage security mitigation technologies that help make it more difficult for attackers to exploit vulnerabilities in a given piece of software. EMET helps to mitigate these vulnerabilities in Internet Explorer on systems where EMET is installed and configured to work with Internet Explorer.

Multiple Elevation of Privilege Vulnerabilities in Internet Explorer

Elevation of privilege vulnerabilities exist when Internet Explorer does not properly validate permissions under specific conditions, potentially allowing script to be run with elevated privileges. The update addresses the vulnerabilities by adding additional permission validations to Internet Explorer.

In a web-based attack scenario, an attacker could host a website that is used to attempt to exploit these vulnerabilities. In addition, compromised websites and websites that accept or host user-provided content could contain specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action. For example, an attacker could trick users into clicking a link that takes them to the attacker's site. An attacker who successfully exploited these vulnerabilities could elevate privileges in affected versions of Internet Explorer.

These vulnerabilities by themselves do not allow arbitrary code to be run. However, these vulnerabilities could be used in conjunction with another vulnerability (e.g., a remote code execution vulnerability) that could take advantage of the elevated privileges when running arbitrary code. For example, an attacker could exploit another vulnerability to run arbitrary code through Internet Explorer, but due to the context in which processes are launched by Internet Explorer, the code might be restricted to run at a low integrity level (very limited permissions). However, an attacker could, in turn, exploit these vulnerabilities to cause the arbitrary code to run at a medium integrity level (permissions of the current user).

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

These vulnerabilities by themselves do not allow arbitrary code to be run. The vulnerabilities would have to be used in conjunction with another vulnerability that allowed remote code execution. For example, an attacker could exploit another vulnerability to run arbitrary code through Internet Explorer, but due to the context in which processes are launched by Internet Explorer, the code might be restricted to run at a low integrity level (very limited permissions). However, an attacker could, in turn, exploit any of these vulnerabilities to cause the arbitrary code to run at a medium integrity level (permissions of the current user).

Workarounds

Microsoft has not identified any workarounds for these vulnerabilities.

Multiple Internet Explorer ASLR Bypass Vulnerabilities

Security feature bypass vulnerabilities exist when Internet Explorer does not use the Address Space Layout Randomization (ASLR) security feature, allowing an attacker to more reliably predict the memory offsets of specific instructions in a given call stack. An attacker who successfully exploited these vulnerabilities could bypass the Address Space Layout Randomization (ASLR) security feature, which helps protect users from a broad class of vulnerabilities. The security feature bypass by itself does not allow arbitrary code execution. However, an attacker could use a ASLR bypass vulnerability in conjunction with another vulnerability, such as a remote code execution vulnerability, that could take advantage of the ASLR bypass to run arbitrary code. For example, a remote code execution vulnerability that is blocked by ASLR, could be exploited after a successful ASLR bypass.

In a web-browsing scenario, successful exploitation of these vulnerabilities requires that a user is logged on and running an affected version of Internet Explorer. Therefore, any systems where a web browser is used frequently, such as workstations or terminal servers, are at the most risk from these vulnerabilities. Servers could be at more risk if administrators allow users to browse and read email on servers. However, best practices strongly discourage allowing this.

The update addresses the vulnerabilities by helping to ensure that affected versions of Internet Explorer properly implement the ASLR security feature.

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Workarounds

An information disclosure vulnerability exists when Internet Explorer does not properly enforce cross-domain policies, which could allow an attacker to gain access to information in another domain or Internet Explorer zone. The update addresses the vulnerability by helping to ensure that cross-domain policies are properly enforced in Internet Explorer.

In a web-based attack scenario, an attacker could host a website that is used to attempt to exploit these vulnerabilities. In addition, compromised websites and websites that accept or host user-provided content could contain specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action. For example, an attacker could trick users into clicking a link that takes them to the attacker's site. An attacker who successfully exploited the vulnerability could view content from another domain or Internet Explorer zone.

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Workarounds

FAQ

I am running Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, or Windows Server 2012 R2. Does this mitigate these vulnerabilities?Yes. By default, Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted web content on a server. This is a mitigating factor for websites that you have not added to the Internet Explorer Trusted sites zone.

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

V1.1 (March 4, 2015): Revised bulletin to clarify what additional updates will be installed, and how they will be installed, when security update 3021952 is installed on systems running Internet Explorer 9, Internet Explorer 10, or Internet Explorer 11. See the Update FAQ for more information. This is an informational change only. There were no changes to the update files. Customers who have already successfully updated their systems do not need to take any action.